May 31, 2007 - Few game series loom as large on the video game scene as Half-Life. The adventures of Gordon Freeman are written in stone in the lexicon of gaming. For those few who may not be familiar with the Half-Life mythos, allow me to explain.

Gordon Freeman, PhD, is a brilliant scientist working in an elite research facility in the American Southwest known simply as The Black Mesa. As the opening unfolds, the player is taken through a labyrinthine series of caverns and ever-deeper shafts below ground level. Gordon's team is experimenting with "anomalous materials" when their research goes horribly wrong. The test-chamber wrenches itself apart as strange lights, explosions, and visions of alien creatures flash before his eyes. It turns out the team has accidentally opened a rift to a dimension of unspeakable power and danger. As Gordon dons his Hazardous EnVironment suit and fights his way to the surface, he encounters a variety of enemies, from mind-controlling "head crabs" and helicopters, to robots and monsters the size of small skyscrapers. It was the basic "what hath science wrought?" plotline, but presented with an unprecedented level of interactivity. The game ended anachronistically, with the reappearance of the enigmatic "G-Man" character, the shadowy figure who may or may not work for the government and appears to be everywhere at once. The G-Man invited Gordon into the void, and everything went black.

Fast-forward six years and Gordon makes his triumphant return in Half-Life 2. Awoken after 20 years in some sort of stasis by the mysterious G-Man, Gordon is introduced into a hellish police state, an almost note-perfect rendition of Orwell's Oceania. All human life is controlled by the Combine, an omnipresent alien race with technology and firepower light-years ahead of humankind. Shortly after Gordon defeated the entity known as the Nihilanth in Half-Life, a cascade of dimensional interference rumbled across the universe and caught the attention of the Combine. They headed to Earth and after a conflict known as "The Seven Hour War," the Combine crushed all human resistance and occupied the planet totally. In order to subjugate the populace, the Combine established central control areas known as Citadels. These massive skyscraper-like fortresses provide a staging area for military operations, transport, and to keep a close eye on humans. They're a chilling high-tech interpretation of the monolithic ministry buildings in "1984." In order to more effectively pillage the Earth's resources and to discourage uprising, the Combine operate a suppression field which renders all humans incapable of reproduction. The intermediary between humans and their intergalactic overlords is the turncoat, Dr. Breen, played with tongue-in-cheek aplomb by Robert Culp.

Life under the combine is grim, but everyone knows their place. It's only when Gordon's return emboldens the burgeoning resistance that things start to fall apart. The player must fight through various cityscapes, seaside fortresses, factories, sewers, and control a variety of weapons and vehicles from a dune-buggy to a swarm of pheromone-crazed arthropods known as Antlions. Along the way several characters from the old game reappeared, including the alien species known as the Vortigaunts, who appear to be just as oppressed by the Combine as humans. One particular Vortigaunt has, like many of his kind, joined the human resistance and assists Gordon in his adventures. The part is voiced by Oscar-winner Louis Gossett Jr., in a turn reminiscent of his performance in "Enemy Mine". Characters like the resistance fighter Alyx and her sweet-tempered robotic brute, Dog, filled the game with color and personality. The storyline ended with the destruction of the main Citadel in City 17 and the defeat of Dr. Breen. Once more, Gordon was encountered by the enigmatic G-Man and the game ended as mysteriously as it began.

The first expansion pack, Episode 1, picked up directly where Half-Life 2 left off. Waking up in a pile of rubble outside the Citadel, Gordon finds that the Citadel is about to undergo a catastrophic meltdown and that the Combine plan to use the event to send a distress signal to their home world. In order to stop the wholesale annihilation of City 17 and to prevent the Combine from calling for backup, Gordon and his companions must re-enter the Citadel and secure the core. After successfully securing the core and delaying the explosion, Gordon and company meet with other resistance fighters attempting to leave City 17 by rail. As hard as they worked to prevent catastrophe, the game ends with the explosion of the citadel, the successful transmission of the combine message, and Alyx in mortal peril. In true operatic form, the second act is always when fall apart. The expansion was received well by the public, if not entirely praised for its short length and hefty price tag. Rather than an additional plot within the confines of Half-Life 2's technology, the game engine had been improved and the graphics were even more impressive than the previous game. It was a satisfying return to the series for gamers who were disappointed by Half-Life 2's abrupt ending and wanted a chance to see more of the inner workings of the Combine.

It's this climate in which Valve is about to release the next installment, Episode Two. A handful of trailers have been released and it appears to represent another small step forward in terms of graphics. The smaller tripods known as "hunters" which were so popular in Episode One will make a return, as well as the ominous "strider" tripods that are synonymous with Half-Life 2. The ever-popular kill-bot with a heart of gold, Dog, will make a clanking, lumbering return, as will Alyx, the Vortigaunt, and several characters from the previous games.

Technologically speaking, the game makes a few simple but important steps forward. The graphics, for example, are even more detailed with greater draw distances, that is, the distance from the player at which characters and environments become fully-rendered. Characters like the striders and the Vortigaunts are rendered with a heightened attention to surface details like metal, skin, eye color, and more dynamic movement. The in-game physics represent a step forward in the technology, something Valve is calling "cinematic physics".

The concept is a bit vague, but it has something to do with creating sequences which will allow the player to experience the physics of events as they happen around them. In order to demonstrate this concept, Valve added a brief bridge-collapse sequence to their teaser trailer. It is available for viewing online and surely ranks among the most realistic and dynamically-rendered video game sequences to date. In the past, when a large event like the destruction of a building or a seismic even occurred, it seemed to be happening in a removed way. The materials collapsed or blew apart in a uniform manner like matchsticks or a child's building blocks. In the sequence from Episode Two, you can feel the initial shockwave, sense the surge of the pavement as it splits and rises before you, and can feel the grind as the girders tear away from the bridge. It's an impressive bit of in-game technology and bodes well for the future of the engine. There's not much else to go on in terms of plot or other specifics, but it looks as if Episode Two will be as much a full game, if not quite as long or involved as Half-Life 2.